package Stack;

import java.util.Arrays;

public class MyStack {
    private int[] elem;
    private int usedSize;
    private static final int DEFAULT_CAPACITY = 10;
    public MyStack(){
        this.elem = new int[DEFAULT_CAPACITY];
    }

    private boolean isFull() {
        return usedSize == elem.length;
    }
    public void push(int val){
        if (isFull()){
            elem = Arrays.copyOf(elem,2*elem.length);
        }
        elem[usedSize] = val;
        usedSize++;
    }
    public boolean isEmpty(){
        return usedSize == 0;
    }

    public int pop(){
        if (isEmpty()){
            throw new EmptyExction( );
        }
        int oldVal = elem[usedSize -1];
        usedSize--;
        return oldVal;
    }

    public int peek(){
        if (isEmpty()){
            throw new RuntimeException();
        }
        return elem[usedSize - 1];
    }
    
}
